1. Field of the Invention
The present invention relates to an electric spindle motor and a disk drive apparatus.
2. Description of the Related Art
Hitherto, a bearing mechanism using a fluid dynamic pressure has been utilized in a motor of a disk drive apparatus. A spindle motor disclosed in Japanese Patent Application Publication No. 2009-136143 includes a shaft, a first bearing component, a second bearing component, and a rotor component. The first bearing component is formed in a cup shape. A lower portion of the shaft is attached in an opening of the first bearing component. The second bearing component is of an annular shape, and is formed integrally with the shaft at an upper end portion of the shaft. The rotor component is disposed within a space defined by the shaft, the first bearing component, and the second bearing component. A fluid dynamic pressure radial bearing portion is formed between a cylindrical surface of the rotor component and an outer circumferential surface of the shaft.
A fluid dynamic pressure thrust bearing portion is formed between a lower surface of the rotor component and a surface of the first bearing component which axially faces the lower surface. A seal gap extending upward is configured in an outer side of the fluid dynamic pressure thrust bearing portion. A pumping seal portion is configured between a lower surface of the second bearing component and a surface of the rotor component which faces the lower surface. Another seal gap extending upward is configured in an outer side of the pumping seal portion.
Incidentally, in the spindle motor disclosed in Japanese Patent Application Publication No. 2009-136143, the motor may not be made thinner when obtaining an axial length of a radial gap and a fastening range between the shaft and the first bearing component. If the shaft and the first bearing component are manufactured as a single component, sufficient shape accuracy of the outer circumferential surface of the shaft may not be obtained because of the resulting complicated shape.